As high-voltage and high-energy density batteries, for example, Li ion batteries are known. The Li ion battery is a cation-based battery utilizing a Li ion as a carrier. Meanwhile, as anion-based batteries, fluoride ion batteries utilizing a fluoride ion as a carrier are known.
For example, Patent Literature 1 discloses a liquid electrolyte for a fluoride ion battery wherein an aromatic material having an aromatic cation and anion is used as a solvent. Also, a metal active material such as Cu is exemplified as an active material. The object of this technique is to provide a liquid electrolyte for a fluoride ion battery that is capable of largely increasing capacity of a battery.
Incidentally, although the technique does not relate to a fluoride ion battery, Patent Literature 2 discloses a cathode active material having a fluoride based perovskite structure represented by MF3 (N is any of Mn, Co, and Ni), and an alkali metal ion battery utilizing the cathode active material. The object of this technique is to provide a cathode active material that has larger discharge potential and energy density (Wh/kg) than those of FeF3. Similarly, although the technique does not relate to a fluoride ion battery, Non-Patent Literature 1 discloses La1.2Sr1.8Mn2O7 as a compound having Ruddlesden-Popper structure.